1. Technical Field
The invention relates to integrating power takeoff equipment with a motor vehicle control system, and more particularly to extend functionality, simplify system modification, improve robustness and optimize fuel usage in a hybrid diesel/electric vehicle platform.
2. Description of the Problem
The use of a hybrid vehicle chassis to support power takeoff (PTO) equipment, such as aerial towers (colloquially called “cherry pickers”), garbage trucks, liquid fuel delivery trucks and the like, is relatively new. Integration of the control of PTO equipment, particularly in a way which best utilizes the fuel reserve of the vehicle, has been given little attention. Were control of the PTO equipment simply carried over from conventional vehicles there would be no operational optimization of the system and the systems would remain highly inflexible.
Many contemporary vehicles are now equipped with body computers, local controllers and controller area networks to implement most aspects of vehicle control. In vehicles designed, built and sold by International Truck and Engine Corporation, an Electrical System Controller (“ESC”) carries out the functions of the body computer. Local controllers which communicate with each other and with the ESC to distribute data and requests essential for operation of local programming by which control is implemented.
In a conventional vehicle only the vehicle's engine is usually capable of meeting the power demands required by PTO equipment. This engine, typically a diesel capable of moving a truck at highway speeds, is designed to provide far more power than is required by the PTO equipment and accordingly is not operated in an optimal manner when the vehicle is supporting PTO operation. The problem is magnified in the environment of an aerial tower vehicle where the vehicle is not moving during PTO operation and PTO operation itself may only be occasional as demanded by an operator. If the engine is kept running much fuel is wasted with the engine idling while waiting for operator inputs and in parasitic losses. In certain types of hybrid configurations the traction motor used for starting the vehicle from a standing start may be available for supporting PTO. Electrical motors suffer far less from parasitic losses than do thermal engines and demand relatively little power input in excess of their output. However, it is not a simple matter of just applying the traction motor to supporting PTO operation. Any operational scheme must take into battery charge status and be able to sustain PTO operation from the thermal engine if required.
Prior art vehicles equipped for PTO operations have typically included an array of relays and extensive hardwiring to support the equipment. This has made the vehicles difficult to modify and subject to hardware failure. Further complicating merged control of the systems is that major subsystems of such a vehicle, particularly a hybrid vehicle come from different manufacturers. For example, in the aerial tower, hybrid vehicle considered in the present application Eaton Corp. supplies the traction motor, transmission, transmission controller, hybrid controller, lithium-ion battery, gear selection controller and inverter; International Truck and Engine supplies the body computer, engine and integrates the components into a vehicle, the chassis mounted PTO equipment may come from a number of sources although the preferred source for an aerial tower is Altec Industries which supplies electromagnetic controlled hydraulic valves, proximity switches, toggle switches, electric motors, relays, solenoids and lights.
The Eaton sub-system consists of modular sub-components installed on the International chassis. Unless coupled, these the subcomponents along with much of the International chassis' system have no clue as to what is going on with the chassis mounted PTO equipment. It is however, absolutely imperative that these systems do know, because it is their job to provide hydraulic and electrical potential to the chassis mounted PTO equipment via the transmission mounted PTO and supporting chassis electrical architecture at the appropriate times and for the appropriate intervals to support precise equipment functionality. Conversely, these systems need to communicate with the chassis mounted PTO equipment for the same reasons previously assigned. The problem created by this communication gap is two fold. The first problem is that the chassis mounted PTO equipment has no way to communicate with the rest of the controllers on the datalink architecture. The second problem is that were the chassis mounted PTO equipment to have a means of communication, what messages would be passed and how would they be formatted? In addition, what systems on the vehicle data bus would listen to on the datalink as it relates to the other control modules and their associated components?